The Wnt/beta-catenin signaling pathway is recognized as one of the key signaling pathways in cancer and as a valid target for therapeutic intervention in many tumor types, especially colon tumors.
The cells of multicellular organisms have the ability to recognize and signal each other, sometimes from fair distances. Such signaling may be accomplished by production of signaling molecules produced by one cell and which subsequently bind to a specific receptor on a different cell. Such signaling pathways have been implicated in various disease processes, including cancer. Wnt signaling, via receptor binding and subsequent increase in intracellular β-catenin, is referred to as the canonical pathway. Wnt proteins form a family of highly conserved secreted signaling molecules that regulate cell-to-cell interactions and have been implicated in cancer pathogenesis. Wnt proteins bind to receptors of the Frizzled and LRP families on the cell surface. Through several cytoplasmic relay components, the signal is transduced to β-catenin, which then enters the nucleus and forms a complex with TCF to activate transcription of Wnt target genes.
In this pathway, Wnt polypeptides is either present on the surface of a signaling cell or released by that cell and eventually contact a specific cell-surface receptor of another cell. Such receptors on target cells include the Frizzled/LRP receptor (LRP=LDL-receptor-related protein) and they transmit a signal to intracellular proteins, such as β-catenin, whose steady-state level is usually kept relatively low through continuous degradation (usually mediated by proteosomes). This is controlled by a complex containing the proteins GSK-3/APC/Axin (GSK-3=glycogen synthase kinase and APC=Adenomatous Polyposis Coli). The result of Wnt-binding at the surface of the target cell is to inhibit β-catenin degradation, whereupon the latter builds up, enters the nucleus and combines with transcriptional regulators to turn on genes.
It has been found that mutations that promote constitutive activation of the Wnt signaling pathway can lead to cancer. [for a review, see Logan and Nusse, “The Wnt Signaling Pathway in Development and Disease,” in Ann. Rev. Cell Dev. Biol., 20:781-810 (2004)] For example, mutations in Axing may predispose an individual to colon cancer (Lammi et al., Am. J. Hum. Genet., 74:1043-50 (2004)). In another such example, familial adenomatous polyposis (FAP), an inherited disease characterized by numerous polyps in the colon and rectum, is often caused by truncation of APC (another Wnt signaling-pathway protein), which promotes aberrant activation of the Wnt pathway. [see: Kinzler et al., Science, 253:661-665 (1991)] Mutations in APC and β-catenin have also be detected in colon cancer and other tumor types (for a review see Giles et al., Biochim. Biophys. Acta, 1653:1-24 (2003)). In addition, mutations in Axin that cause loss of function have been identified in hepatocellular carcinomas. [see: Satoh et al., Nat. Genet., 24:245-50 (2000)] Thus, any mutation or other cellular event that serves to decouple Wnt signaling and β-catenin regulation appears to be important in producing cancer.
Because such cancer-genesis events have been linked to elevated levels of β-catenin (i.e., situations where β-catenin levels are Wnt independent), small organic compounds and other agents that serve to re-establish this linkage or otherwise reduce β-catenin would prove useful in abating the cancerous process and find use as anti-neoplastic agents. The present invention provides such agents in the form of disulfonamide derivatives of fluorene, anthracene, xanthene, dibenzosuberone and acridine that reduce levels of beta-catenin in tumor cells.
Structurally related fluorene and anthracene derivatives with the sulfonamide groups substituted with aromatic amines are known in the art (see, for example, US 2004/0019042) as inhibitors of P2X3 and P2X2/3 containing receptors and have been found useful in the treatment and prevention of disorders such as bladder overactivity, urinary incontinence or pain. However, herein it is shown that novel structurally related compounds can be prepared and used as modulators of the Wnt/β-catenin pathway. It is known that β-catenin is a regulator of the Wnt signally pathway. (see Willert and Nusse, Current Opinion in Genetics and Development, 8:95-102 (1998).